On the North? Always?

  I remember as a child, one should look for moss on trees to help you figure out which way is north and from there you can get an idea of which way to go.  Then the other night, I was rewatching NCIS and the medical examiners arrived late because the driver thought moss grew on the south side.  Ducky replied that only applied in the southern hemisphere.

That comment made me wonder if it was true?   People say the Coriolis effect has water swirling one direction in the north and the other way in the south, so why wouldn't moss grow on the opposite side of the tree.

This idea has been around for a very long time and has probably been handed down from generation to generation.   So the question is why does moss seem to grow only on the north side of the tree? 

Moss is a simple plant that likes to grow in shade.  The way the planet works is that the further north from the equator you travel, the more shade you are likely to get on the north side and in they same way, the further south you go from the equator, the more shade is found on the south side of the tree.

Furthermore, moss need moisture because moss are unable to circulate water around, the cells have to have immediate access to water and the plant also needs it to reproduce.   Again the north  or southern sides make it more likely the moss will find everything it needs to survive.

But that is not the full story.  Moss only tend to grow more on the north or south side but if the conditions are right, moss can be found any where on the tree as long as there is shade and water.  Which is why you may find moss growing on rocks, fallen logs, or anywhere else proper conditions are found.

In addition, the surface has to be such that water slows enough for the moss to absorb and use the moisture.  This is one reason you may not see moss on certain rocks, or trees while they are on others or higher off the ground than in other situations.

So now you know, its not always found on the north or south side.  It is found where ever the conditions are proper for moss to grown.  Let me know what you think, I'd love to hear. Have a great day.